Studies of six-coordinate adducts all-trans-[M(OAr)2(X)2(L)2] (M=Nb, Ta; X=Cl, Br; L=tertiary phosphine, pyridine)

Schweiger, Scott W.; Freeman, Emily; Clark, Janet R.; Potyen, Mark C.; Fanwick, Phillip E.; Rothwell, Ian P.

doi:10.1016/s0020-1693(00)00195-x

Cited by 4 publications

(2 citation statements)

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“…The assignment of an all-trans geometry is based upon previously isolated phosphine complexes . Also the direct d 1 -group 5 analogues [M(OC 6 H 3 Pr i 2 -2,6) 2 Cl 2 (py) 2 ] (M = Nb, Ta) have been reported and fully characterized (crystallographic inversion center) 1 Temperature Dependence of the 1 H NMR Chemical Shifts of the 4- tert -Butylpyridine Signals in [W(OC 6 HPh 4 -2,3,5,6) 2 Cl 2 (py-Bu t -4) 2 ] temp (°C)δ ortho-H (ppm)δ meta-H (ppm)δ Bu t (ppm) 95 −30.99 14.85 0.58 85 −31.52 14.75 0.52 75 −32.04 14.64 0.45 65 −32.62 14.51 0.38 55 −33.18 14.39 0.31 45 −33.75 14.26 0.24 35 −34.32 14.11 0.16 25 −34.92 13.96 0.09 15 −35.50 13.80 0.01 5 −36.06 13.63 −0.08 −5 −36.63 13.45 −0.16 −15 −37.21 13.27 −0.25 …”

Section: Resultsmentioning

confidence: 99%

Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η⁵-Cyclohexadienyl Group

2003

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The sodium amalgam reduction (2 Na per W) of hydrocarbon solutions of [W(OC6HPh4-2,3,5,6)2Cl4] in the presence of pyridine or 4-tert-butylpyridine leads to the W(IV) compounds [W(OC6HPh4-2,3,5,6)2Cl2(py)2] (1) and [W(OC6HPh4-2,3,5,6)2Cl2(4-tert-butylpyridine)2] (2) in good yields. The ambient-temperature 1H NMR spectra of both 1 and 2 were found to be sharp and to exhibit extensive contact shifts due to the paramagnetic tungsten center. The addition of 2,2‘-bipyridine to an emerald green solution of [W(OC6HPh3-η6-C6H5)(OC6HPh4-2,3,5,6)(PEt3)] produced [W(OC6HPh4-2,3,5,6)2(bipy)2] (3), containing two bipy rings and two terminal aryloxide ligands coordinated mutually cis. The W−N(bipy) distances of 2.092(2), 2.093(2), 2.096(2), and 2.115(2) Å in 3 are among the shortest so far reported for bipy ligands bound to either molybdenum or tungsten. The solid state and solution data for 3 indicate that reduction of both bipy ligands has occurred, but whether this involves four-electron reduction to yield d0-W(VI) is unclear. The addition of 4-tert-butylpyridine to [W(OC6HPh3-η6-C6H5)(OC6HPh4-2,3,5,6)(PEt3)] was found (1H NMR) to lead only to partial substitution of the phosphine ligand to produce [W(OC6HPh3-η6-C6H5)(OC6HPh4-2,3,5,6)(py-But-4)] (4). The sodium amalgam reduction (4 Na per W) of hydrocarbon solutions of [W(OC6HPh4-2,3,5,6)2Cl4] in the presence of 4-tert-butylpyridine produced a mixture found to contain the expected compound 4 along with a new salt compound, [W(OC6HPh3-η5-C6H6)(OC6HPh3-η1-C6H4)(OC6HPh4-2,3,5,6)][Cl] (5), containing a total of three aryloxide ligands. Crystals were obtained containing a 1:1 ratio of 4/5. One of the aryloxides in 5 is terminally bound, the second is cyclometalated, while the third chelates to the metal center via an η5-interaction with an ortho-cyclohexadienyl ring. The formal oxidation state of the metal center in 5 is (VI), and the unit cell contains one chloride ion to balance the positive charge on the tungsten. In compound 5 the hydride ligand formed via the cyclometalation has been transferred to the ortho-position of a phenyl ring. The structural parameters for the π-bound rings in 4 and 5 and their relevance to catalytic arene hydrogenation are discussed.

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Section: Resultsmentioning

confidence: 99%

Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η⁵-Cyclohexadienyl Group

2003

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“…Although the literature contains voluminous reports on phenoxides of main group elements, transition metals, lanthanides, and actinides, more recent interest has centered on the early and late d-block metal chemistry supported by sterically bulky aryloxide ligation [5][6][7]. Niobium complexes, in particular, derived from alcohols and substituted phenols [8,9] present striking structural features and a wide range of applications in material science [10][11][12][13][14][15]. The niobium(V) catalysts bearing di-and tri-phenolic ligands polymerize ethylene, in the presence of an organoaluminum cocatalyst [16].…”

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confidence: 99%

Synthesis, characterization, and acceptor behavior of dichlorotris(2-t-butylphenoxo)niobium(V)

Sharma

Bhatt

et al. 2010

Journal of Coordination Chemistry

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The reaction of niobium pentachloride with three equivalents of 2-t-butylphenol in carbon tetrachloride afforded [NbCl 2 (OC 6 H 4 C(CH 3 ) 3 -2) 3 ]. The identity of the complex has been established by elemental analyses, molar conductance, molecular weight determination, IR, 1 H, and 13 C-NMR and UV-Vis spectral studies. Based upon these studies, a square-pyramidal geometry around niobium has been proposed. Thermal behavior of the complex has been studied by TGA and DTA. Acceptor behavior of [NbCl 2 (OC 6 H 4 C(CH 3 ) 3 -2) 3 ] toward Ph 3 P, Ph 3 As, Ph 3 PO, Ph 3 AsO, and an uncommon ligand arsenictrithiophenoxide As(SPh) 3 allows the isolation of 1 : 1 addition compounds as shown by physicochemical, IR, and 1 H-NMR spectral studies. The formation of [NbCl 2 (OC 6 H 4 C(CH 3 ) 3 -2) 3 ] Á As(SPh) 3 appears to be the first adduct of its class and suggests the suitability of As(SPh) 3 as a ligand.

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Niobium and Tantalum

Waters

Wedd

Ziółek

et al. 2003

Comprehensive Coordination Chemistry II

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Studies of six-coordinate adducts all-trans-[M(OAr)2(X)2(L)2] (M=Nb, Ta; X=Cl, Br; L=tertiary phosphine, pyridine)

Cited by 4 publications

References 34 publications

Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η⁵-Cyclohexadienyl Group

Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η⁵-Cyclohexadienyl Group

Synthesis, characterization, and acceptor behavior of dichlorotris(2-t-butylphenoxo)niobium(V)

Niobium and Tantalum

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Studies of six-coordinate adducts all-trans-[M(OAr)2(X)2(L)2] (M=Nb, Ta; X=Cl, Br; L=tertiary phosphine, pyridine)

Cited by 4 publications

References 34 publications

Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η5-Cyclohexadienyl Group

Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η5-Cyclohexadienyl Group

Synthesis, characterization, and acceptor behavior of dichlorotris(2-t-butylphenoxo)niobium(V)

Niobium and Tantalum

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Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η⁵-Cyclohexadienyl Group

Low-Valent Tungsten Aryloxide Compounds with Pyridine Ancillary Ligation: Intramolecular Reduction of Heterocyclic and Aromatic Rings Including Formation of an η⁵-Cyclohexadienyl Group